Aspects of spin dynamics and magnetic interactions

Non-collinear magnetic alignment is somewhat unusual for equilibrium and th ese systems exhibiting such ground states are frequently 'victims' of compe ting forces. For non-equilibrium or dynamical systems (e.g. T > 0) non-coll inear alignment is universal. We discuss such systems and present some basi c formalism for evaluating from first principles the equation of motion and related relevant properties. Considerable discussion is also devoted to ob taining from first principles, parameters for model magnetic Hamiltonians. These models represent a convenient way to gain insight and to approximatel y evaluate magnetic interactions for very complex systems. (C) 1999 Elsevie r Science B.V. All rights reserved.